Synthesis mechanism of BaTi₄O₉ nanopowder doped with Pr in liquid-phase

Doping Pr BaTi₄O₉ nanopowder was prepared by sol-gel method. Through analyzing dry gel thermal treated at different temperatures, the possible synthesis mechanism of Pr doped BaTi₄O₉ powder was discussed. At first, Ti(OC₄H₉)₄ hydrolyzes and three dimensional networks form, in which Ba²⁺ and CH₃COO^- are mostly in the form of ions; organic solvent is gradually volatilized through calefaction at 700°C, then the offspring is turned into BaTi₅O₁₁. With the temperature increasing to 850°C, BaTi₅O₁₁ begins resolving partly and forming BaTi₄O₉, and at 1000°C Ba₄Ti₁₃O₂₂ forms partly, but BaTi₄O₉ is the main crystal phase. BaTi₅O₁₁ and Ba₄Ti₁₃O₃₀ decomposes completely at 1200° and forms single-phase BaTi₄O₉. The infrared (IR) analysis also shows that the absorbing peak of Ti-O bond is not in the characteristic absorption range of Ti-O-Ti (700-900 cm^-1), but slightly shifted to the higher end (908 cm^-1). It is probably because that doping Pr enters into the crystal lattice and causes the abnormal absorption of Ti-O bond.